1. Field of the Invention
Embodiments of the invention relate to an autostereoscopic display and a control method thereof.
2. Discussion of the Related Art
As the stereoscopic image reproduction technology is applied to display devices, such as a television and a monitor, now is the age in which people can view 3D stereoscopic images even at home. A 3D display may be classified into a stereoscopic display and an autostereoscopic display called a glasses-free 3D display. The stereoscopic display displays a parallax image between the left and right eyes on a direct-view display or a projector through changes in a polarization direction of the parallax image or in a time-division manner and thus implements a stereoscopic image using polarization glasses or liquid crystal shutter glasses. The autostereoscopic display implements the stereoscopic image by generally installing an optical element, such as a parallax barrier and a lenticular lens, for separating an optical axis of the parallax image in front of a display screen.
The 3D display may be manufactured based on an active matrix liquid crystal display. The active matrix liquid crystal display comprises a thin film transistor (TFT) as a switching element of pixel. Liquid crystal cells of the active matrix liquid crystal display change a transmittance based on a difference between a data voltage supplied to a pixel electrode and a common voltage supplied to a common electrode, thereby displaying an image.
Because the liquid crystal display is not a self-emission element, a separate light source such as a backlight unit is necessary. The liquid crystal display may cause a reduction in image quality, for example, motion blur because of slow response characteristics of liquid crystals. To prevent the reduction in image quality resulting from the slow response characteristics of the liquid crystals, the backlight unit may be driven based on a blinking driving technology or a scanning backlight driving technology. In the blinking driving technology, light sources of the backlight unit are simultaneously turned on and off.
In the scanning backlight driving technology, a light emitting area of the backlight unit is divided into a plurality of backlight blocks, and the backlight blocks each including the light sources are sequentially turned on along a data scanning direction of the liquid crystal display panel.
A technology has been recently proposed to implement the autostereoscopic display using a switchable 3D element, such as a switchable lens and a switchable barrier, in which a barrier or a lens is not fixed and is electrically controllable. The switchable 3D element includes a liquid crystal layer and electrodes applying an electric signal to the liquid crystal layer and thus may electrically control liquid crystal molecules. The switchable 3D element was disclosed in U.S. Patent Application Nos. 2011/0242442 and 2012/0154556 filed by the present applicant.
The blinking driving technology simultaneously turns on and off the light sources of the backlight unit, which provide light to the entire screen of the liquid crystal display panel, based on response characteristic of liquid crystals positioned in the center of the liquid crystal display panel. When the blinking driving technology is applied to the autostereoscopic display including the switchable 3D element, 3D crosstalk is generated at upper and lower sides of the liquid crystal display panel because of a difference between liquid crystal response times of the liquid crystal display panel and the switchable 3D element on the upper and lower sides of the liquid crystal display panel and a difference between addressing timing of left and right eye image data and the liquid crystal response time. The 3D crosstalk is a phenomenon in which the 3D image appears as overlaid images of an image (hereinafter referred to as ‘left eye recognition image’) perceived through the viewer's left eye and an image (hereinafter referred to as ‘right eye recognition image’) perceived through the viewer's right eye.
The scanning backlight driving technology sequentially drives the light sources of the backlight unit by preset backlight block unit. The scanning backlight driving technology may be applied to the autostereoscopic display including the switchable 3D element. The pixel data is sequentially addressed to pixels of the liquid crystal display panel in a direction from the upper side to the lower side of the liquid crystal display panel. Hence, the liquid crystals of the liquid crystal display panel sequentially respond in the direction from the upper side to the lower side of the liquid crystal display panel. The backlight blocks of the backlight unit are sequentially turned on and off in synchronization with the response of the liquid crystal display panel. As a result, a motion picture response time (MPRT) and the 3D crosstalk may be improved. However, even when the scanning backlight driving technology is applied to the autostereoscopic display including the switchable 3D element, the switchable 3D element is simultaneously turned on and off on the entire screen of the liquid crystal display panel. Hence, a luminance difference depending on a position of the screen and the 3D crosstalk are is generated because of a difference between liquid crystal response times of the liquid crystal display panel and the switchable 3D element and a difference between the liquid crystal response times of the liquid crystal display panel and the switchable 3D element and turn-on and turn-off times of the backlight unit.